This invention relates in general to monitoring systems for chemical laboratories and more particularly to safety systems for crystal growth facilities.
There are a series of experiments scheduled to be conducted at the upcoming Space Station, in outer space. Some of these involve the Space Station's Furnace Facility. They will require monitoring systems to ensure successful experiments, as well as limit the possible hazards to the Space Station and crew. For example, the first furnace facility scheduled for operation will be the crystal growth furnace. Experiments there will center on the crystal growth of inorganic compounds.
In crystal growth operations on Earth, ampoules are typically used to house the components and reaction product. As the initial components are heated during the reaction process, they change phases and the pressure can build dramatically within the fragile ampoule. For example, when pure liquid arsenic is mixed with metal gallium to form gallium arsenide, GaAs, the heated arsenic changes from liquid to gas prior to reaction. This causes the pressure increase, up to about five-to-ten-fold. Rupture of ampoules are therefore common. The contamination problem is reduced on Earth because of gravity and dilution of the gaseous vapors (here, poisonous arsenic)into the atmosphere.
The ampoule rupture problem increases in severity in the Space Station Furnace Facility as the crystal growth furnace reaches its maximum temperature of 1350.degree. C. In order to diminish to possibility of inorganic material escaping the furnace containment area, the ampoule is scheduled to be surrounded by a metal canister (as is sometimes used on Earth). However, this canister has the potential to be breached and, if that occurs unlike on Earth, there is nowhere for the gases to be vented. The minimum requirement would be for the entire furnace facility to be sealed and returned to the Earth for decontamination.
Accordingly, it is a general object of the present invention to provide a simple, fast method for determining an ampoule rupture in crystal growth formations at the Space Station.
It is another general object to provide an early detection technique to indicate ampoule rupture, prior to a canister being breached.
It is a more specific object to provide a monitoring system that will automatically shut off the crystal growth furnace if an ampoule ruptures, thereby reducing the internal pressure and maintaining canister containment.
It is yet another to provide a safety device that, while designed for space, has commercial application in the crystal growth field on Earth.